The human leukemias and non-Hodgkin's lymphomas are currently diagnosed and classified primarily using morphologic criteria. It is now recognized, however, that in many instances routine morphologic studies of tissue sections and blood or bone marrow smears do not provide sufficient information for accurate diagnosis and precise classification of these neoplasms. Immunologic marker studies have demonstrated that many of the morphologic entities are functionally heterogeneous and can be separated into immunologically homogeneous groups. In one entity, acute lymphoblastic leukemia, this recently acquired knowledge has already been shown to have prognostic significance. Cytogenetic analysis has been shown to provide prognostically significant information about leukemias. Preliminary data from a new technique, flow analysis of DNA content, have indicated that this rapid and quantitative methodology can be used to distinguish between neoplastic and non-neoplastic cell populations in many instances. In addition, flow analysis of DNA distributions provides data about the relative percentages of cells in each phase of the cell cycle, which may be of benefit in determining the growth rate and clinical aggressiveness of these neoplasms. We propose to study malignant lymphomas and leukemias provided from our own institution and a number of hospitals in the cummunity by a combination of methodologies including immunologic surface marker studies, cytogenetics and flow microfluorometry in conjunction with routine morphology in order to investigate their value in providing earlier detection and more precise diagnosis and classification of these diseases. The results of these studies will be correlated with the clinical behavior, response to therapy, and length of survival. The findings should provide the basis for the development of more effective treatment protocols.